Question

A boy throws a ball vertically up . it returns to the ground after 5 seconds . find :
i. the maximum height reached by the ball.
ii. the velocity with which the ball is thrown up

please give short answer.

Answer 1

Answer:

i) 31.25 m

ii)25 m/s

Explanation:

First, we will look at all the values that are given to us:

t = 5s

a = -10m/s^2

Now, let's try and calculate the velocity with which the ball is thrown up

We know that when the ball is at its top height, the velocity is 0. So, v=0.

We know that the force of gravity acting on the ball = -10 m/s

We know that time taken is 2.5s because it returns to the ground after 5s.

So we will use the 1st equation of motion: v = u + at to calculate initial velocity u

Now, let's plug in the values in the equation: 0 = u + -10*2.5

Now we can use simple algebra to figure out u

We will get -u = -25. The minus signs cancel out and we are left with u =25 m/s.

You have got the answer to your second question. Now let's try and solve the first question.

Now again let's write our values

u = 25 m/s

a = -10 m/s^2

v=  0 m/s

t= 2.5 s

Now, we will use 2nd equation of motion to figure out the maximum distance.

S =ut + 1/2*at^2

Let's plug in our values.

s = 25 * 2.5 + 1/2* -10 * 2.5 *2.5

We will use simple algebra to figure out s.

We will be left with s = 31.25 m

So now you have got your answers.

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